[27508] in bugtraq
Re: Ambiguities in TCP/IP - firewall bypassing
daemon@ATHENA.MIT.EDU (Alun Jones)
Fri Oct 18 19:04:09 2002
Message-Id: <4.3.2.7.2.20021018162423.01d80ea8@208.55.91.110>
Date: Fri, 18 Oct 2002 16:28:25 -0500
To: benjamin@seattleFenix.net
From: Alun Jones <alun@texis.com>
In-Reply-To: <20021018205515.GA27861@surreal.seattlefenix.net>
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At 03:55 PM 10/18/2002, Benjamin Krueger wrote:
> One could also make a case for continuing to abide by the cardinal
>rule "Be permissive in what you accept, and strict in what you send".
>Tough call, but its difficult to justify describing stacks that are
>permissive as "highly bogus" or "lazy" given that being permissive in
>what you accept is an established notion.
If a usage makes any kind of sense, then it has usually been allowed.
>Compliant by the letter, if questionably in spirit. I'm not aware of any
>tcp client systems that would send SynFin in the real world, so a stack
>that responded with RST could arguably be "more" correct (for example).
Not necessarily. Have you heard of T/TCP? Before that was around, I
remember hearing discussion of using a packet with SYN, FIN, and data all
in one, to cut down on round-trips in really short communications, while
still providing reliability.
One of the lessons you learn when writing / reading RFC material is that
"there are more things on heaven and earth, Horatio, than are dreamt of in
your philosophy" (or thereabouts). Just because _you_ don't see a use for
a feature, that doesn't mean to say that someone else won't / can't, and
specifically, it isn't usually worth limiting a protocol for the rather
arbitrary reason that you can't see how a feature would be used.
Alun.
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